In recent years, as environment-friendly electric wires that do not use any polyvinyl chloride or halogen-based flame retardant, the use of eco-material (EM) electric wires and cables has been rapidly spreading.
These eco-material electric wires and cables are demanded to contain no halogen element or toxic heavy metal, as well as to have flame retardancy and generate only a limited amount of corrosive gas or smoke when combusted.
For example, as a standard for eco-material electric wires and cables, IEC 60754-1 (JIS C3612) has been set. In addition, IEC 60754-2 (JIS C3666-2) has been set for methods of measuring the electric conductivity and the acidity of a gas generated during combustion, and IEC 60695-6-30 (JIS C60695-6-30) has been set for methods of measuring the smoke density. These standards prescribe the amount of corrosive gas generation and the smoke density.
Furthermore, flame retardancy is prescribed in, for example, the flame retardancy standard of the U.S. Underwriters Laboratories, Inc. (UL Standard).
In the above-described eco-material electric wire and cable applications, as a halogen-free resin, a polyolefin-based resin containing polyethylene as a main component is mainly used. Further, in order to impart flame retardancy, a metal hydroxide such as aluminum hydroxide or magnesium hydroxide is used as a halogen-free flame retardant (see Patent Documents 1 and 2).